This effective Hamiltonian describes the ground state of nickelates at zero
or low doping. It is similar to the usual \(t\) -\(J\)  model for cuprates [1]}, but includes two types of mobile quasiparticles: doublons
(Kondo singlets) and holons. It is now clear why the self-doping can
efficiently suppress the AF long-range order to yield a paramagnetic ground
state in nickelates. At high temperatures, doublons become deconfined,
causing incoherent Kondo scattering in transport measurements. This is
confirmed by the resistivity replotted in Fig. REF  as a
function of temperature for both NdNiO\(_{2}\)  and LaNiO\(_{2}\) . Unlike cuprates, the resistivity exhibits metallic behavior at high temperature but
shows an upturn below about 70 K. If we put the data on a linear-log scale,
we find that the upturn follows exactly a logarithmic temperature (\(\ln T\) )
dependence over a large temperature range for both compounds, which is a
clear evidence for incoherent Kondo scattering typical for low carrier
density Kondo systems [2]}. The saturation at very low
temperatures is an indication of Kondo screening. This Kondo scenario is also
supported by the Hall measurement. In both compounds, the Hall coefficient \(R_{H}\)  exhibits non-monotonic temperature dependence. It approaches a negative constant at high temperatures due to the contribution of conduction electrons, but exhibits the same \(\ln T\)  dependence at low
temperatures. The linear relation \(R_{H}\propto \rho \)  is an indication of
skew scattering by localized magnetic impurities in typical Kondo systems
[3]}, [4]}.
